This invention relates to techniques, systems and devices that are used to characterize, measure, monitor and/or evaluate the blood glucose level of a patient, for example, a human. More particularly, in one aspect, the present invention measures, monitors and/or evaluates, in a non-invasive manner, the glucose concentration in the aqueous humor of the eye as a way of monitoring blood glucose levels of a patient.
More than ten million people in the United States of America suffer from diabetic hyperglycemia (an increased level of glucose in the blood) and hypoglycemia (a reduced level of glucose in the blood). Individuals afflicted with either disease in a severe form typically perform an invasive blood glucose level analysis four or more times a day. Typically, such an analysis requires the patient to do a finger or forearm stick to remove blood. Thereafter, the blood is placed on an electrochemical sensor or enzymatic-based colorimetric strip to determine the glucose level.
A significant disadvantage of this conventional technique is that it is “invasive”—in that the technique often entails extraction of a small amount of blood from the patient's finger or a forearm stick. This invasive technique is painful, embarrassing, opens the body to infection, and may ultimately result in less frequent monitoring which, in turn, results in poor or insufficient glucose monitoring and control.
Recently a device known as a “GlucoWatch” has been introduced to the market that is based on a principle of reverse iontophoresis. Reverse iontophoresis senses glucose containing fluid through the skin of the patient. The GlucoWatch typically requires a reading be taken every 20 minutes to obtain glucose “trending” information, which may be employed to monitor the patient's blood glucose level.
Several polarmetric optical approaches to non-invasive glucose detection have been proposed (See, for example, U.S. Pat. Nos. 5,209,231; 5,398,681; 5,448,992; 5,457,535; 5,448,992; 5,671,301; 5,788,632; 6,188,477; 6,370,407; and 6,246,893). While these systems and techniques are non-invasive, and as such, do not include the “pain” that accompanies an “invasive” system and technique, these non-invasive systems and techniques have numerous shortcomings including, for example, problems or shortcoming with addressing the “adverse” impact of eye motion or artifact, corneal birefringence, and/or limited sensitivity and specificity of blood glucose level measurement and monitoring accuracy.
There is a need for a non-invasive (or minimally invasive) system, device and technique that overcomes one, some or all of shortcomings of the conventional techniques. For example there is a need for a non-invasive (or minimally invasive) system, device and technique that relatively accurately measures, monitors, characterizes and/or evaluates the blood glucose level of a patient. Moreover, there is a need for an improved optically based system, device and technique that measures, monitors, characterizes and/or evaluates the blood glucose level of a patient that overcomes, addresses or minimizes the “adverse” impact of eye motion or artifact and/or corneal birefringence.